I'm not a plumber but you say they exist so a good start might be the local Home Depot, Lowe's, or the like. If they don't have them, look in the YELLOW PAGES under PLUMBING SUPPLIES. Plumbing Supply Houses I'm SURE have what you want if you want to go there directly. There is a similiar unit for washing machines where the water lines go into it.
I'm sorry I don't have the exact answer you're looking for. My best to ya and hope this helps.